bridge: Fix possibly wrong MLD queries' ethernet source address

bridge: Fix possibly wrong MLD queries' ethernet source address

BugLink: http://bugs.launchpad.net/bugs/769042

[ Upstream commit a7bff75b087e7a355838a32efe61707cfa73c194 ]

The ipv6_dev_get_saddr() is currently called with an uninitialized
destination address. Although in tests it usually seemed to nevertheless
always fetch the right source address, there seems to be a possible race
condition.

Therefore this commit changes this, first setting the destination
address and only after that fetching the source address.

Reported-by: Jan Beulich <JBeulich@novell.com>
Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>